Spring_MVC(2)控制层处理

言归正传，研究一下注解下的控制层。
我习惯于使用JSTL展示页面，因此需要在原lib基础上增加jstl.jar和standard.jar，详细lib依赖如下：

引用

aopalliance-1.0.jar
commons-logging-1.1.1.jar
log4j-1.2.15.jar
spring-beans-2.5.6.jar
spring-context-2.5.6.jar
spring-context-support-2.5.6.jar
spring-core-2.5.6.jar
spring-tx-2.5.6.jar
spring-web-2.5.6.jar
spring-webmvc-2.5.6.jar
standard.jar
jstl.jar

上一篇文中，我们定义了控制器AccountController：
AccountController.java

/**
 * 2010-1-23
 */
 package org.zlex.spring.controller;

 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.ServletRequestUtils;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.zlex.spring.service.AccountService;

 /**
 *
 * @author <a href="mailto:[email protected]">梁栋</a>
 * @version 1.0
 * @since 1.0
 */
 @Controller
 @RequestMapping("/account.do")
 public class AccountController {

     @Autowired
     private AccountService accountService;

     @RequestMapping(method = RequestMethod.GET)
     public void hello(HttpServletRequest request, HttpServletResponse response)
             throws Exception {

        String username = ServletRequestUtils.getRequiredStringParameter(
                 request, "username");
        String password = ServletRequestUtils.getRequiredStringParameter(
                 request, "password");
        System.out.println(accountService.verify(username, password));
    }
}

/**
 * 2010-1-23
 */
package org.zlex.spring.controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.ServletRequestUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.zlex.spring.service.AccountService;

/**
 * 
 * @author <a href="mailto:[email protected]">梁栋</a>
 * @version 1.0
 * @since 1.0
 */
@Controller
@RequestMapping("/account.do")
public class AccountController {

	@Autowired
	private AccountService accountService;

	@RequestMapping(method = RequestMethod.GET)
	public void hello(HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		String username = ServletRequestUtils.getRequiredStringParameter(
				request, "username");
		String password = ServletRequestUtils.getRequiredStringParameter(
				request, "password");
		System.out.println(accountService.verify(username, password));
	}
}

先说注解@RequestMapping
这里使用注解@RequestMapping(method = RequestMethod.GET)指定这个方法为get请求时调用。同样，我们可以使用注解@RequestMapping(method = RequestMethod.POST)指定该方法接受post请求。

@Controller
 @RequestMapping("/account.do")
 public class AccountController {

     @RequestMapping(method = RequestMethod.GET)
     public void get() {
    }

     @RequestMapping(method = RequestMethod.POST)
     public void post() {
    }
}

@Controller
@RequestMapping("/account.do")
public class AccountController {

	@RequestMapping(method = RequestMethod.GET)
	public void get() {
	}

	@RequestMapping(method = RequestMethod.POST)
	public void post() {
	}
}

这与我们久别的Servlet很相像，类似于doGet()和doPost()方法！
我们也可以将其改造为多动作控制器，如下代码所示：

@Controller
 @RequestMapping("/account.do")
 public class AccountController {

     @RequestMapping(params = "method=login")
     public void login() {
    }

     @RequestMapping(params = "method=logout")
     public void logout() {
    }

@Controller
@RequestMapping("/account.do")
public class AccountController {

	@RequestMapping(params = "method=login")  
	public void login() {
	}

	@RequestMapping(params = "method=logout")  
	public void logout() {
	}

这样，我们可以通过参数“method”指定不同的参数值从而通过请求（"/account.do?method=login"和"/account.do?method=logout"）调用不同的方法！
注意：使用多动作控制器必须在配置文件中加入注解支持！

<bean
         class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />

<bean
		class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />

当然，我们也可以将注解@RequestMapping指定到某一个方法上，如：

@Controller
 public class AccountController {

     @RequestMapping("/a.do")
     public void a() {}

     @RequestMapping("/b.do")
     public void b() {}
}

@Controller
public class AccountController {
	
	@RequestMapping("/a.do")
	public void a() {}

	@RequestMapping("/b.do")
	public void b() {}
}

这样，请求“a.do”和“b.do”将对应不同的方法a() 和b()。这使得一个控制器可以同时承载多个请求！
@RequestMapping("/account.do")是@RequestMapping(value="/account.do")的简写！
再说输入参数！
这里的方法名可以随意定义，但是参数和返回值却又要求！
为什么？直接看源代码，我们就能找到答案！
AnnotationMethodHandlerAdapter.java部分源代码——有关参数部分：

@Override
 protected Object resolveStandardArgument(Class parameterType, NativeWebRequest webRequest)
         throws Exception {

    HttpServletRequest request = (HttpServletRequest) webRequest.getNativeRequest();
    HttpServletResponse response = (HttpServletResponse) webRequest.getNativeResponse();

     if (ServletRequest.class.isAssignableFrom(parameterType)) {
         return request;
    }
     else if (ServletResponse.class.isAssignableFrom(parameterType)) {
         this.responseArgumentUsed = true;
         return response;
    }
     else if (HttpSession.class.isAssignableFrom(parameterType)) {
         return request.getSession();
    }
     else if (Principal.class.isAssignableFrom(parameterType)) {
         return request.getUserPrincipal();
    }
     else if (Locale.class.equals(parameterType)) {
         return RequestContextUtils.getLocale(request);
    }
     else if (InputStream.class.isAssignableFrom(parameterType)) {
         return request.getInputStream();
    }
     else if (Reader.class.isAssignableFrom(parameterType)) {
         return request.getReader();
    }
     else if (OutputStream.class.isAssignableFrom(parameterType)) {
         this.responseArgumentUsed = true;
         return response.getOutputStream();
    }
     else if (Writer.class.isAssignableFrom(parameterType)) {
         this.responseArgumentUsed = true;
         return response.getWriter();
    }
     return super.resolveStandardArgument(parameterType, webRequest);
}

		@Override
		protected Object resolveStandardArgument(Class parameterType, NativeWebRequest webRequest)
				throws Exception {

			HttpServletRequest request = (HttpServletRequest) webRequest.getNativeRequest();
			HttpServletResponse response = (HttpServletResponse) webRequest.getNativeResponse();

			if (ServletRequest.class.isAssignableFrom(parameterType)) {
				return request;
			}
			else if (ServletResponse.class.isAssignableFrom(parameterType)) {
				this.responseArgumentUsed = true;
				return response;
			}
			else if (HttpSession.class.isAssignableFrom(parameterType)) {
				return request.getSession();
			}
			else if (Principal.class.isAssignableFrom(parameterType)) {
				return request.getUserPrincipal();
			}
			else if (Locale.class.equals(parameterType)) {
				return RequestContextUtils.getLocale(request);
			}
			else if (InputStream.class.isAssignableFrom(parameterType)) {
				return request.getInputStream();
			}
			else if (Reader.class.isAssignableFrom(parameterType)) {
				return request.getReader();
			}
			else if (OutputStream.class.isAssignableFrom(parameterType)) {
				this.responseArgumentUsed = true;
				return response.getOutputStream();
			}
			else if (Writer.class.isAssignableFrom(parameterType)) {
				this.responseArgumentUsed = true;
				return response.getWriter();
			}
			return super.resolveStandardArgument(parameterType, webRequest);
		}

也就是说，如果我们想要在自定义的方法中获得一些个“标准”输入参数，参数类型必须包含在以下类型中：

引用

ServletRequest
ServletResponse
HttpSession
Principal
Locale
InputStream
OutputStream
Reader
Writer

当然，上述接口其实都是对于HttpServletRequest和HttpServletResponse的扩展。
此外，我们还可以定义自己的参数。
注意：自定义参数必须是实现类，绝非接口！Spring容器将帮你完成对象初始化工作！
比如说上文中，我们需要参数username和password。我们可以这么写：

@RequestMapping(method = RequestMethod.GET)
 public void hello(String username,String password) {
    System.out.println(accountService.verify(username, password));
}

	@RequestMapping(method = RequestMethod.GET)
	public void hello(String username,String password) {
		System.out.println(accountService.verify(username, password));
	}

如果参数名不能与这里的变量名保持一致，那么我们可以使用注解@RequestParam进行强制绑定，代码如下所示：

@RequestMapping(method = RequestMethod.GET)
 public void hello(@RequestParam("username") String u,
         @RequestParam("password") String p) {
    System.out.println(accountService.verify(u, p));
}

	@RequestMapping(method = RequestMethod.GET)
	public void hello(@RequestParam("username") String u,
			@RequestParam("password") String p) {
		System.out.println(accountService.verify(u, p));
	}

这比起我们之前写的代码有所简洁：

@RequestMapping(method = RequestMethod.GET)
 public void hello(HttpServletRequest request, HttpServletResponse response)
         throws Exception {

    String username = ServletRequestUtils.getRequiredStringParameter(
             request, "username");
    String password = ServletRequestUtils.getRequiredStringParameter(
             request, "password");
    System.out.println(accountService.verify(username, password));
}

	@RequestMapping(method = RequestMethod.GET)
	public void hello(HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		String username = ServletRequestUtils.getRequiredStringParameter(
				request, "username");
		String password = ServletRequestUtils.getRequiredStringParameter(
				request, "password");
		System.out.println(accountService.verify(username, password));
	}

ServletRequestUtils类的工作已经由Spring底层实现了，我们只需要把参数名定义一致即可，其内部取参无需关心！
除了传入参数，我们还可以定义即将传出的参数，如加入ModelMap参数：

@SuppressWarnings("unchecked")
 @RequestMapping(method = RequestMethod.GET)
 public Map hello(String username, String password, ModelMap model) {

    System.out.println(accountService.verify(username, password));

     model.put("msg", username);

     return model;
}

	@SuppressWarnings("unchecked")
	@RequestMapping(method = RequestMethod.GET)
	public Map hello(String username, String password, ModelMap model) {

		System.out.println(accountService.verify(username, password));
		
		model.put("msg", username);

		return model;
	}

这时，我们没有定义页面名称，Spring容器将根据请求名指定同名view，即如果是jap页面，则account.do->account.jsp！
不得不承认，这样写起来的确减少了代码量！
接着说输出参数！
通过ModelMap，我们可以绑定输出到的页面的参数，但最终我们将要返回到何种页面呢？再次查看AnnotationMethodHandlerAdapter源代码！
AnnotationMethodHandlerAdapter.java部分源代码——有关返回值部分：

@SuppressWarnings("unchecked")
 public ModelAndView getModelAndView(Method handlerMethod, Class handlerType, Object returnValue,
        ExtendedModelMap implicitModel, ServletWebRequest webRequest) {

     if (returnValue instanceof ModelAndView) {
        ModelAndView mav = (ModelAndView) returnValue;
        mav.getModelMap().mergeAttributes(implicitModel);
         return mav;
    }
     else if (returnValue instanceof Model) {
         return new ModelAndView().addAllObjects(implicitModel).addAllObjects(((Model) returnValue).asMap());
    }
     else if (returnValue instanceof Map) {
         return new ModelAndView().addAllObjects(implicitModel).addAllObjects((Map) returnValue);
    }
     else if (returnValue instanceof View) {
         return new ModelAndView((View) returnValue).addAllObjects(implicitModel);
    }
     else if (returnValue instanceof String) {
         return new ModelAndView((String) returnValue).addAllObjects(implicitModel);
    }
     else if (returnValue == null) {
         // Either returned null or was 'void' return.
         if (this.responseArgumentUsed || webRequest.isNotModified()) {
             return null;
        }
         else {
             // Assuming view name translation...
             return new ModelAndView().addAllObjects(implicitModel);
        }
    }
     else if (!BeanUtils.isSimpleProperty(returnValue.getClass())) {
         // Assume a single model attribute...
         ModelAttribute attr = AnnotationUtils.findAnnotation(handlerMethod, ModelAttribute.class);
         String attrName = (attr != null ? attr.value() : "");
         ModelAndView mav = new ModelAndView().addAllObjects(implicitModel);
         if ("".equals(attrName)) {
            Class resolvedType = GenericTypeResolver.resolveReturnType(handlerMethod, handlerType);
            attrName = Conventions.getVariableNameForReturnType(handlerMethod, resolvedType, returnValue);
        }
         return mav.addObject(attrName, returnValue);
    }
     else {
         throw new IllegalArgumentException("Invalid handler method return value: " + returnValue);
    }
}

		@SuppressWarnings("unchecked")
		public ModelAndView getModelAndView(Method handlerMethod, Class handlerType, Object returnValue,
				ExtendedModelMap implicitModel, ServletWebRequest webRequest) {

			if (returnValue instanceof ModelAndView) {
				ModelAndView mav = (ModelAndView) returnValue;
				mav.getModelMap().mergeAttributes(implicitModel);
				return mav;
			}
			else if (returnValue instanceof Model) {
				return new ModelAndView().addAllObjects(implicitModel).addAllObjects(((Model) returnValue).asMap());
			}
			else if (returnValue instanceof Map) {
				return new ModelAndView().addAllObjects(implicitModel).addAllObjects((Map) returnValue);
			}
			else if (returnValue instanceof View) {
				return new ModelAndView((View) returnValue).addAllObjects(implicitModel);
			}
			else if (returnValue instanceof String) {
				return new ModelAndView((String) returnValue).addAllObjects(implicitModel);
			}
			else if (returnValue == null) {
				// Either returned null or was 'void' return.
				if (this.responseArgumentUsed || webRequest.isNotModified()) {
					return null;
				}
				else {
					// Assuming view name translation...
					return new ModelAndView().addAllObjects(implicitModel);
				}
			}
			else if (!BeanUtils.isSimpleProperty(returnValue.getClass())) {
				// Assume a single model attribute...
				ModelAttribute attr = AnnotationUtils.findAnnotation(handlerMethod, ModelAttribute.class);
				String attrName = (attr != null ? attr.value() : "");
				ModelAndView mav = new ModelAndView().addAllObjects(implicitModel);
				if ("".equals(attrName)) {
					Class resolvedType = GenericTypeResolver.resolveReturnType(handlerMethod, handlerType);
					attrName = Conventions.getVariableNameForReturnType(handlerMethod, resolvedType, returnValue);
				}
				return mav.addObject(attrName, returnValue);
			}
			else {
				throw new IllegalArgumentException("Invalid handler method return value: " + returnValue);
			}
		}
	}

返回值的定义十分庞大，或者说可怕的if-else多少有点让我觉得厌恶！
我们可以定义以下类型的返回值：

引用

ModelAndView
Model
View
Map
String
null

ModelAndView、Model和View都是Spring之前版本所特有的元素，Map对应于传入参数ModelMap，String定义页面名称，null即对应void类型方法！
最常用的实现方式如下：

@SuppressWarnings("unchecked")
 @RequestMapping(method = RequestMethod.GET)
 public String hello(String username, String password, ModelMap model) {

    System.out.println(accountService.verify(username, password));

     model.put("msg", username);

     return "account";
}

	@SuppressWarnings("unchecked")
	@RequestMapping(method = RequestMethod.GET)
	public String hello(String username, String password, ModelMap model) {

		System.out.println(accountService.verify(username, password));

		model.put("msg", username);

		return "account";
	}

当然，对于我来说在返回值中写入这么一个字符串多少有点不能接受，于是我还是乐于使用输入参数ModelMap+输出参数Map的方式。
给出一个完整的AccountController实现：
AccountController.java

/**
 * 2010-1-23
 */
 package org.zlex.spring.controller;

 import java.util.Map;

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.ModelMap;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.zlex.spring.service.AccountService;

 /**
 *
 * @author <a href="mailto:[email protected]">梁栋</a>
 * @version 1.0
 * @since 1.0
 */
 @Controller
 @RequestMapping("/account.do")
 public class AccountController {

     @Autowired
     private AccountService accountService;

     @SuppressWarnings("unchecked")
     @RequestMapping(method = RequestMethod.GET)
     public Map hello(String username, String password, ModelMap model) {

        System.out.println(accountService.verify(username, password));

         model.put("msg", username);
         return model;
    }
}

/**
 * 2010-1-23
 */
package org.zlex.spring.controller;

import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.zlex.spring.service.AccountService;

/**
 * 
 * @author <a href="mailto:[email protected]">梁栋</a>
 * @version 1.0
 * @since 1.0
 */
@Controller
@RequestMapping("/account.do")
public class AccountController {

	@Autowired
	private AccountService accountService;

	@SuppressWarnings("unchecked")
	@RequestMapping(method = RequestMethod.GET)
	public Map hello(String username, String password, ModelMap model) {

		System.out.println(accountService.verify(username, password));

		model.put("msg", username);
		return model;
	}
}

最后说注解@Session
如果想将某个ModelMap中的参数指定到Session中，可以使用@Session注解，将其绑定为Session熟悉，代码如下所示：

@Controller
 @RequestMapping("/account.do")
 @SessionAttributes("msg")
 public class AccountController {

     @Autowired
     private AccountService accountService;

     @SuppressWarnings("unchecked")
     @RequestMapping(method = RequestMethod.GET)
     public Map hello(String username, String password, ModelMap model) {

        System.out.println(accountService.verify(username, password));

         model.put("msg", username);
         return model;
    }

}

@Controller
@RequestMapping("/account.do")
@SessionAttributes("msg")
public class AccountController {

	@Autowired
	private AccountService accountService;

	@SuppressWarnings("unchecked")
	@RequestMapping(method = RequestMethod.GET)
	public Map hello(String username, String password, ModelMap model) {

		System.out.println(accountService.verify(username, password));

		model.put("msg", username);
		return model;
	}

}

当然，我们还需要配置一下对应的视图解析器，给出完整配置：
servelt.xml

<?xml version="1.0" encoding="UTF-8"?>
 <beans
     xmlns="http://www.springframework.org/schema/beans"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns:p="http://www.springframework.org/schema/p"
     xmlns:context="http://www.springframework.org/schema/context"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
         http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
     <context:component-scan
         base-package="org.zlex.spring.controller" />
     <bean
         id="urlMapping"
         class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" />
     <bean
         class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />
     <bean
         id="jstlViewResolver"
         class="org.springframework.web.servlet.view.InternalResourceViewResolver"
         p:viewClass="org.springframework.web.servlet.view.JstlView"
         p:prefix="/WEB-INF/page/"
         p:suffix=".jsp" />
 </beans>

<?xml version="1.0" encoding="UTF-8"?>
<beans
	xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
	<context:component-scan
		base-package="org.zlex.spring.controller" />
	<bean
		id="urlMapping"
		class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" />
	<bean
		class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />
	<bean
		id="jstlViewResolver"
		class="org.springframework.web.servlet.view.InternalResourceViewResolver"
		p:viewClass="org.springframework.web.servlet.view.JstlView"
		p:prefix="/WEB-INF/page/"
		p:suffix=".jsp" />
</beans>

这里使用了JstlView作为视图解析器。同时，指定前缀路径为"/WEB-INF/page/"，后缀路径为".jsp"。也就是说，Spring容器将会在这个路径中寻找匹配的jsp文件！
注意加入xmlns:p="http://www.springframework.org/schema/p"命名空间！
再给出页面内容：
taglib.jsp

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
 <%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
 <%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql"%>
 <%@ taglib prefix="x" uri="http://java.sun.com/jsp/jstl/xml"%>
 <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%>
 <%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
 <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
<%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql"%>
<%@ taglib prefix="x" uri="http://java.sun.com/jsp/jstl/xml"%>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>

account.jap

<%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"<spa

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Spring_MVC(3)表单页面处理 | Spring_MVC(1)构建简单web应用

• 2010-04-24 18:42
• 浏览 993
• 评论(3)
• 分类:企业架构
• 相关推荐

评论

3 楼 liutao1600 2013-05-07  

学习了，太好了

2 楼 tamsiuloong 2010-06-28  

UTF

tamsiuloong 写道

楼主你好，我是基于下面配置的urlMpping
<bean id="urlMapping"
class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">

<property name="mappings">
<props>
<prop key="site/site.do">siteAction</prop>
</bean>
如果我也想使用基于注解的控制器，我应该怎样做？

同时使用二者，可以吗？

1 楼 tamsiuloong 2010-06-28  

楼主你好，我是基于下面配置的urlMpping
<bean id="urlMapping"
class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">

<property name="mappings">
<props>
<prop key="site/site.do">siteAction</prop>
</bean>
如果我也想使用基于注解的控制器，我应该怎样做？

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